export const CONTENT_MANIFEST_SCHEMA_VERSION = 1;

export interface ContentManifestFile {
  readonly packId: string;
  readonly url: string;
  readonly sha256: string;
  readonly bytes: number;
  readonly download?: {
    readonly url: string;
    readonly encoding: "gzip";
    readonly sha256: string;
    readonly bytes: number;
  };
}

export interface ContentManifestPack {
  readonly id: string;
  readonly label: string;
  readonly bytes: number;
  readonly downloadBytes?: number;
  readonly fileCount: number;
  readonly bundledOnAndroid: boolean;
  readonly dependencies: readonly string[];
}

export interface ContentManifest {
  readonly schemaVersion: number;
  readonly version: string;
  readonly createdAt: string;
  readonly minimumAppVersion: string;
  readonly packs: readonly ContentManifestPack[];
  readonly files: Readonly<Record<string, ContentManifestFile>>;
}

/** Resolves runtime logical asset URLs to the independently installable packs that own them. */
export function contentPackIdsForLogicalUrls(
  manifest: ContentManifest,
  logicalUrls: readonly string[],
): readonly string[] {
  const packIds = new Set<string>();
  for (const logicalUrl of logicalUrls) {
    let pathname: string;
    try {
      pathname = new URL(logicalUrl, "https://healer-man.invalid").pathname;
    } catch {
      throw new Error(`Invalid content asset URL: ${logicalUrl}`);
    }
    const entry = manifest.files[pathname];
    if (!entry) throw new Error(`The content catalog is missing randomized asset ${pathname}.`);
    packIds.add(entry.packId);
  }
  return [...packIds].sort();
}

function isRecord(value: unknown): value is Record<string, unknown> {
  return Boolean(value) && typeof value === "object" && !Array.isArray(value);
}

export function parseContentManifest(value: unknown): ContentManifest {
  if (!isRecord(value) || value.schemaVersion !== CONTENT_MANIFEST_SCHEMA_VERSION) {
    throw new Error("This content catalog uses an unsupported schema.");
  }
  if (typeof value.version !== "string" || typeof value.createdAt !== "string" || typeof value.minimumAppVersion !== "string") {
    throw new Error("The content catalog is missing version information.");
  }
  if (!Array.isArray(value.packs) || !isRecord(value.files)) {
    throw new Error("The content catalog is malformed.");
  }
  const packs = value.packs.map((pack) => {
    if (!isRecord(pack)
      || typeof pack.id !== "string"
      || typeof pack.label !== "string"
      || typeof pack.bytes !== "number"
      || typeof pack.fileCount !== "number"
      || typeof pack.bundledOnAndroid !== "boolean"
      || !Array.isArray(pack.dependencies)
      || !pack.dependencies.every((dependency) => typeof dependency === "string")) {
      throw new Error("The content catalog contains a malformed pack.");
    }
    return pack as unknown as ContentManifestPack;
  });
  const files = Object.fromEntries(Object.entries(value.files).map(([logicalPath, entry]) => {
    if (!logicalPath.startsWith("/")
      || !isRecord(entry)
      || typeof entry.packId !== "string"
      || typeof entry.url !== "string"
      || !/^[a-f0-9]{64}$/.test(String(entry.sha256))
      || typeof entry.bytes !== "number"
      || !Number.isSafeInteger(entry.bytes)
      || entry.bytes < 0) {
      throw new Error(`The content catalog contains a malformed file: ${logicalPath}`);
    }
    if (entry.download !== undefined && (!isRecord(entry.download)
      || entry.download.encoding !== "gzip"
      || typeof entry.download.url !== "string"
      || !/^[a-f0-9]{64}$/.test(String(entry.download.sha256))
      || !Number.isSafeInteger(entry.download.bytes)
      || Number(entry.download.bytes) < 0)) {
      throw new Error(`The content catalog contains a malformed compressed file: ${logicalPath}`);
    }
    return [logicalPath, entry as unknown as ContentManifestFile];
  }));
  return { ...value, packs, files } as unknown as ContentManifest;
}

function numericVersion(value: string): readonly number[] {
  const match = /^(\d+)\.(\d+)\.(\d+)/.exec(value.trim());
  return match ? [Number(match[1]), Number(match[2]), Number(match[3])] : [0, 0, 0];
}

export function appVersionMeetsMinimum(current: string, minimum: string): boolean {
  const left = numericVersion(current);
  const right = numericVersion(minimum);
  for (let index = 0; index < 3; index += 1) {
    if (left[index] > right[index]) return true;
    if (left[index] < right[index]) return false;
  }
  return true;
}

type ContentPackFiles = readonly (readonly [string, ContentManifestFile])[];
const packFileIndexes = new WeakMap<ContentManifest["files"], ReadonlyMap<string, ContentPackFiles>>();
const EMPTY_PACK_FILES: ContentPackFiles = [];

/** Catalog file maps are immutable; index once instead of scanning during gameplay. */
export function filesForContentPack(
  manifest: ContentManifest,
  packId: string,
): readonly (readonly [string, ContentManifestFile])[] {
  let index = packFileIndexes.get(manifest.files);
  if (!index) {
    const groups = new Map<string, [string, ContentManifestFile][]>();
    for (const [logicalPath, entry] of Object.entries(manifest.files)) {
      let files = groups.get(entry.packId);
      if (!files) {
        files = [];
        groups.set(entry.packId, files);
      }
      files.push([logicalPath, entry]);
    }
    for (const files of groups.values()) files.sort(([left], [right]) => left.localeCompare(right));
    index = groups;
    packFileIndexes.set(manifest.files, index);
  }
  return index.get(packId) ?? EMPTY_PACK_FILES;
}

export interface ContentFileIdentity {
  readonly sha256: string;
}

export function changedFilesForPack(
  manifest: ContentManifest,
  packId: string,
  activeFiles: Readonly<Record<string, ContentFileIdentity>>,
): readonly (readonly [string, ContentManifestFile])[] {
  return filesForContentPack(manifest, packId).filter(([logicalPath, entry]) => (
    activeFiles[logicalPath]?.sha256 !== entry.sha256
  ));
}